1. Statement of the Technical Field
This invention relates generally to security tags and associated detachers and, more particularly, to a security tag and a security tag detacher for use in an electronic article surveillance (EAS) system.
2. Description of the Related Art
Electronic article surveillance systems are well known in the art and are used for inventory control and to prevent theft and similar unauthorized removal of articles from a controlled area. Typically, in such systems a system transmitter and a system receiver are used to establish a surveillance zone which must be traversed by any articles being removed from the controlled area.
An EAS security tag is affixed to each article and includes a marker or sensor adapted to interact with a signal being transmitted by the system transmitter into the surveillance zone. This interaction causes a further signal to be established in the surveillance zone which further signal is received by the system receiver. Accordingly, upon movement of a tagged article through the surveillance zone, a signal will be received by the system receiver, identifying the unauthorized presence of the tagged article in the zone.
Certain types of EAS security tags have been designed to be reusable and, thus, include releasable attachment devices for affixing the tags to the articles. Such attachment devices are further designed to be releasable by authorized personnel only so that unauthorized removal of a tag from its article is avoided. To this end, many attachment devices are made releasable only through the use of an associated special tool or detaching mechanism.
Attachment devices for EAS security tags include a wide variety of different latching mechanisms designed to prevent unauthorized personnel from removing the pin from the tag. The stimulus needed to unlatch an EAS security tag will depend upon the particular latching mechanism in use. Accordingly, a variety of different detaching units utilize various means to separate reusable, removable EAS security tags from articles of merchandise. Known systems for unlatching EAS security tags include devices generally involve the application of a force to certain latching components. The force can be applied directly to latching components by means of a mechanical element (e.g. by means of a probe inserted into the tag). Other detaching systems have powerful magnets which apply a magnetic force to latching components, thereby unlatching the tag. The mechanical and magnetic detaching methods are the two main types of systems commonly used with hard EAS security tags. Regardless of how the force is applied, the result is a disengagement of a latching element with an attachment pin in the tag, thereby allowing the tag to be removed from the article.
In tags which require a magnetic stimulus for unlatching, the latching mechanism (such as a moving clamp or pin) is usually made with a magnetic material such as carbon steel. Upon exposure to a magnetic field from a detacher unit, part of the clamp is attracted to the detacher. This movement of the latching components allows the pin of an EAS tag to be unlocked from the tag housing, thereby allowing the item to which the tag was attached to be removed from the store without setting off an alarm. In order to prevent illegitimate tag detachment using a commonly available magnet, the tag's clamp is typically designed such that it can only be opened when exposed to an unusually high magnetic field.
In the case of tags which are designed for unlatching in response to a mechanically applied force, a detacher probe structure is often used to interact with the tag. Examples of these types of mechanical detaching units are disclosed in U.S. Pat. Nos. 5,426,419; 5,528,914; 5,535,606, and 5,955,951. (The disclosures of these patents are incorporated herein by reference.). The detaching unit is operated to insert a probe or hook into the enclosure portion of the tag to release a latch or clamp. The pin may then be released from the enclosure portion of the tag, and the tag removed from the article of merchandise.